1. Field of the Invention
The present invention relates to new polymers that contain oxygen and/or sulfur alicyclic (heteroalicyclic) units and use of such polymers as a resin binder component for photoresist compositions, particularly chemically-amplified positive-acting resists that can be effectively imaged at short wavelengths such as sub-200 nm, particularly 193 nm.
2. Background
Photoresists are photosensitive films used for transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable reagents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For a positive-acting photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less developer soluble. Photoresist compositions are described in Deforest, Photoresist Materials and Processes, McGraw Hill Book Company, New York, ch. 2, 1975 and by Moreau, Semiconductor Lithography, Principles, Practices and Materials, Plenum Press, New York, ch. 2 and 4.
More recently, chemically-amplified-type resists have been increasingly employed, particularly for formation of sub-micron images and other high performance applications. Such photoresists may be negative-acting or positive-acting and generally include many crosslinking events (in the case of a negative-acting resist) or deprotection reactions (in the case of a positive-acting resist) per unit of photogenerated acid. In the case of positive chemically-amplified resists, certain cationic photoinitiators have been used to induce cleavage of certain xe2x80x9cblockingxe2x80x9d groups pendant from a photoresist binder, or cleavage of certain groups that comprise a photoresist binder backbone. See, for example, U.S. Pat. Nos. 5,075,199; 4,968,581; 4,883,740; 4,810,613; and 4,491,628, and Canadian Patent Application 2,001,384. Upon cleavage of the blocking group through exposure of a coating layer of such a resist, a polar functional group is formed, e.g., carboxyl or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer. See also R. D. Allen et al., Proceedings of SPIE, 2724:334-343 (1996); and P. Trefonas et al. Proceedings of the 11th International Conference on Photopolymers (Soc. Of Plastics Engineers), pp 44-58 (Oct. 6, 1997).
While currently available photoresists are suitable for many applications, current resists also can exhibit significant shortcomings, particularly in high performance applications such as formations of highly resolved sub-half micron and sub-quarter micron features.
Consequently, interest has increased in photoresists that can be photoimaged with short wavelength radiation, including exposure radiation of about 250 nm or less, or even about 200 nm or less, such as wavelengths of about 248 nm (provided by KrF laser) or 193 nm (provided by an ArF exposure tool). See European Published Application EP915382A2. Use of such short exposure wavelengths can enable formation of smaller features. Accordingly, a photoresist that yields well-resolved images upon 248 nm or 193 nm exposure could enable formation of extremely small (e.g. sub-0.25 xcexcm) features that respond to constant industry demands for smaller dimension circuit patterns, e.g. to provide greater circuit density and enhanced device performance.
However, many current photoresists are generally designed for imaging at relatively higher wavelengths, such as G-line (436 nm) and I-line (365 nm) are generally unsuitable for imaging at short wavelengths such as sub-200 nm. Even shorter wavelength resists, such as those effective at 248 nm exposures, also are generally unsuitable for sub-200 nm exposures, such as 193 nm imaging.
More specifically, current photoresists can be highly opaque to extremely short exposure wavelengths such as 193 nm, thereby resulting in poorly resolved images.
It thus would be desirable to have new photoresist compositions, particularly resist compositions that can be imaged at short wavelengths such as sub-200 nm exposure wavelengths, particularly 193 nm.
We have now found novel polymers and photoresist compositions that comprise the polymers as a resin binder component. The photoresist compositions of the invention can provide highly resolved relief images upon exposure to extremely short wavelengths, particularly sub-200 nm wavelengths such as 193 nm.
Polymers of the invention contain a oxygen- and/or sulfur-containing heteroalicyclic ring that is preferably fused to the polymer backbone (i.e. at least two heteroalicyclic ring atoms as part of the polymer backbone). The heteroalicyclic ring has one or more oxygen and/or sulfur atoms as ring members.
Preferred polymers of the invention also contain a carbon alicyclic group (i.e. the group has all carbon ring members) that is fused to the polymer backbone, i.e. the carbon alicyclic ring has at least two carbon ring members that comprise the polymer backbone. Preferred fused carbon alicyclic groups are provided by polymerization of cyclic olefin (endocyclic double bond) compounds such as optionally substituted norbornene groups. We have found that incorporation of such carbon alicyclic groups into a polymer can significantly increase plasma etch resistance of a photoresist containing the polymer.
Preferred heteroalicyclic polymer units may be substituted, e.g. by heteroalkyl groups such as ethers (alkoxy) preferably having 1 to about 10 carbon atoms, alkylthio preferably having 1 to about 10 carbon atoms, alkylsulfinyl preferably 1 to about 10 carbon atoms, alkylsulfonyl preferably having 1 to about 10 carbon atoms, and the like. It has been surprising found that such substituents can provide enhanced lithographic results, particularly enhanced substrate adhesion.
For use in photoresist compositions, polymers of the invention also will contain one or more units that comprise photoacid-labile moieties. The photoacid-labile group may be a substituent of one or more of the above-mentioned units, such as a substituent of a polymerized vinyl alicyclic ether, vinyl alicyclic thioether or carbon alicyclic group. The photoacid labile moiety also may be present as an additional polymer unit, e.g. as a polymerized alkyl acrylate or alkylmethacrylate, particularly an acrylate having an alicyclic moiety such as methyladamantyl acrylate or methyladamantyl methacrylate. Preferred alicyclic photoacid-labile moieties are tertiary ester alicyclic hydrocarbon groups that have two or more fused or bridged rings. Preferred tertiary ester groups include optionally substituted adamantyl, particularly methyl adamantyl as mentioned above; optionally substituted fencyl groups, particularly ethyl fencyl; optionally substituted pinanyl; and optionally substituted tricyclo decanyl, particularly an alkyl-substituted tricyclo decanyl such as 8-ethyl-8-tricyclodecanyl e.g. as provided by polymerization of 8-ethyl-8-tricyclodecanyl acrylate and 8-ethyl-8-tricyclodecanyl methacrylate. Additional alicyclic ester groups also will be suitable, including additional bicyclic, tricyclic and other polycyclic moieties.
Polymers of the invention also may contain units in addition to the above groups. For example, polymers of the invention also may contain nitrile units such as provided by polymerization of methacrylonitrile and acrylonitrile. Additional contrast enhancing groups also may be present in polymers of the invention, such as groups provided by polymermization of methacrylic acid, acrylic acid, and such acids protected as photoacid labile esters, e.g. as provided by reaction of ethoxyethyl methacrylate, t-butoxy methacrylate, t-butylmethacrylate and the like.
Generally preferred polymers of the invention contain 3, 4 or 5 distinct repeat units, i.e. preferred are terpolymers, tetrapolymers and pentapolymers that contain one or more heteroalicyclic groups as disclosed herein.
Polymers of the invention are preferably employed in photoresists imaged at 193 nm, and thus preferably will be substantially free of any phenyl or other aromatic groups. For example, preferred polymers contain less than about 5 mole percent aromatic groups, more preferably less than about 1 or 2 mole percent aromatic groups, more preferably less than about 0.1, 0.02, 0.04 and 0.08 mole percent aromatic groups and still more preferably less than about 0.01 mole percent aromatic groups. Particularly preferred polymers are completely free of aromatic groups. Aromatic groups can be highly absorbing of sub-200 nm radiation and thus are undesirable for polymers used in photoresists imaged with such short wavelength radiation.
The invention also provides methods for forming relief images, including methods for forming a highly resolved relief image such as a pattern of lines where each line has essentially vertical sidewalls and a line width of about 0.40 microns or less, and even a width of about 0.25, 0.20 or 0.16 microns or less. The invention further provides articles of manufacture comprising substrates such as a microelectronic wafer substrate or liquid crystal display or other flat panel display substrate having coated thereon a polymer, photoresist or resist relief image of the invention. Other aspects of the invention are disclosed infra.
As discussed above, polymers of the invention contain a heteroalicyclic ring that is preferably fused to a polymer backbone. The fused heterocyclic ring units contain one. or more oxygen and/or sulfur atoms. By stating herein that a cyclic group is fused to a polymer backbone, it is meant that two ring members of the cyclic group, typically two adjacent carbon atoms of the cyclic group, are also part of the polymer backbone. Such a fused ring can be provided by polymerizing a cyclic monomer that has an endocyclic double bond.
Preferred oxygen ring polymer units will be free of other hetero atoms such as sulfur (i.e. only oxygen and carbon ring members). Typically, the oxygen ring unit will contain a single oxygen ring atom and may have one or more ring substituents. As discussed above, it has been found that such ring substituents can significantly enhance substrate adhesion.
Additionally, an oxygen heteroalicyclic group will be present in a polymer together with polymerized carbon alicyclic compounds such as optionally substituted norbornene. As referred to herein, the term xe2x80x9ccarbon alicyclic groupxe2x80x9d means each ring member of the non-aromatic group is carbon. The carbon alicyclic group can have one or more endocyclic carbon-carbon double bonds, provided the ring is not aromatic.
Preferred polymers of the invention that contain oxygen heteroalicyclic units comprise a structure of the following Formula I: 
wherein X, Y, and each Z are each independently carbon or oxygen, with at least one of X, Y or Z being oxygen, and preferably no more than two of X, Y and Z being oxygen;
Q represents an optionally substituted carbon alicyclic ring fused to the polymer backbone (i.e. two Q ring members being adjacent carbons of the polymer backbone); the alicyclic ring suitably having from about 5 to about 18 carbon atoms and is suitably a single ring (e.g. cyclopentyl, cyclohexyl or cycloheptyl), or more preferably Q is polycyclic e.g. and contain 2, 3, 4 or more bridged, fused or otherwise linked rings, and preferred substituents of a substituted Q group include photoacid-labile moieties such as a photoacid-labile ester;
each R is the same or different non-hydrogen substituent such as cyano; optionally substituted alkyl preferably having 1 to about 10 carbon atoms; optionally substituted alkanoyl preferably having 1 to about 10 carbon atoms; optionally substituted alkoxy preferably having 1 to about 10 carbon atoms; optionally substituted alkylthio preferably having 1 to about 10 carbon atoms; optionally substituted alkylsulfinyl preferably 1 to about 10 carbon atoms; optionally substituted alkylsulfonyl preferably having 1 to about 10 carbon atoms; optionally substituted carboxy preferably have 1 to about 10 carbon atoms (which includes groups such as xe2x80x94COORxe2x80x2 where Rxe2x80x2 is H or C1-8alkyl, including esters that are substantially non-reactive with photoacid); a photoacid-labile group such as a photoacid-labile ester e.g. a tert-butyl ester and the like; etc.
m is 1 (to provide a fused five-membered ring), 2 (to provide a fused six-membered ring), 3 (to provide a fused seven-membered ring), or 4 (to provide a fused eight-membered ring);
n is an integer of from 0 (i.e. no R ring substituents), 1 (i.e. a single R ring substituent) to the maximum possible value permitted by the valences of the ring members, and preferably n is 0, 1, 2, 3, 4 or 5, and more preferably n is 0, 1, 2 or 3;
p is the mole fraction of the fused oxygen ring units based on total units in the polymer; and r is the mole fraction of the fused carbon alicyclic ring units based on total units in the polymer, and p and r are each greater than zero.
As discussed above, preferred carbon alicyclic ring units are polymerized optionally substituted norbornene groups. Thus, preferred polymers that contain oxygen heteroalicyclic units comprise a structure of the following Formula IA: 
wherein X, Y, Z, R, m and n are the same specified for Formula I above;
R1 and R2 are each independently hydrogen or a non-hydrogen substituent such as halo (F, Cl, Br, I), nitro, cyano, optionally substituted alkyl (including cycloalkyl) preferably having from 1 to about 16 carbons; optionally substituted alkoxy preferably having from 1 to about 16 carbons; optionally substituted alkylthio preferably having from 1 to about 16 carbons; optionally substituted carboxy preferably have 1 to about 10 carbon atoms (which includes groups such as xe2x80x94COORxe2x80x2 where Rxe2x80x2 is H or C1-8alkyl, including esters that are substantially non-reactive with photoacid); a lactone; an anhydride such as an itaconic anhydride group; a photoacid-labile group such as a photoacid-labile ester, particularly a photoacid-labile ester moiety with a tertiary alicyclic group or a non-cyclic group such as t-butyl; and the like, or Rxe2x80x2 and R2 may be taken together to form one or more rings fused to the depicted norbornyl ring;
p is the mole fraction of the fused oxygen ring units based on total units in the polymer; and r is the mole fraction of the fused optionally substituted norbornene ring units based on total units in the polymer, and p and r are each greater than zero.
Particularly preferred oxygen ring polymer units include those that have five or six ring members and an oxygen ring member adjacent to the polymer backbone. Accordingly, preferred are polymers that comprise a structure of the following Formula IB: 
wherein each Zxe2x80x2 is independently oxygen, sulfur or carbon, and preferably each Zxe2x80x2 is carbon; mxe2x80x2 is 1, 2, 3 or 4; and R and n are each the same as defined in Formula I above, and preferably n is 0, 1, 2, 3, 4 or 5, and more preferably n is 0, 1, 2 or 3;
Q is the same as defined in Formula I;
p is the mole fraction of the fused oxygen ring units based on total units in the polymer; and r is the mole fraction of the fused carbon alicyclic ring units based on total units in the polymer, and p and r are each greater than zero.
Preferred polymers of Formula IB contain polymerized norbornene units, e.g. polymers that comprise a structure of the following Formula IC: 
wherein Zxe2x80x2, mxe2x80x2, R, n, and p are the same as defined in Formula IB; and
R1, R2 and r are the same as defined in Formula IA.
Preferred sulfur ring polymer units also will be free of other hetero atoms such as oxygen (i.e. only sulfur and carbon ring members), or will contain only one or two other hetero atoms such as oxygen, typically only one additional heteroatom such as oxygen.
Preferred sulfur ring polymer units include those of the following Formula II: 
wherein X, Y, and each Z are each independently carbon, oxygen or sulfur, with at least one of X, Y or Z being sulfur, and preferably no more than two of X, Y and Z being sulfur;
each R is the same or different non-hydrogen substituent such as cyano; optionally substituted alkyl preferably having 1 to about 10 carbon atoms; optionally substituted alkanoyl preferably having 1 to about 10 carbon atoms; optionally substituted alkoxy preferably having 1 to about 10 carbon atoms; optionally substituted alkylthio preferably having 1 to about 10 carbon atoms; optionally substituted alkylsulfinyl preferably 1 to about 10 carbon atoms; optionally substituted alkylsulfonyl preferably having 1 to about 10 carbon atoms; optionally substituted carboxy preferably have 1 to about 10 carbon atoms (which includes groups such as xe2x80x94COORxe2x80x2 where Rxe2x80x2 is H or C1-8alkyl, including esters that are substantially non-reactive with photoacid); a photoacid-labile group such as a photoacid-labile ester e.g. a tert-butyl ester and the like; etc.
m is 1 (to provide a fused five-membered ring), 2 (to provide a fused six-membered ring), 3 (to provide a fused seven-membered ring) or 4 (to provide a fused eight-membered ring);
n is an integer of 0 (no R substituents present), 1 (i.e. a single R ring substituent) to the maximum possible substitution permitted by the valences of the ring members, and preferably n is 0, 1, 2, 3, 4 or 5, and more preferably n is 0, 1, 2 or 3; and
p is greater than zero and is the mole fraction of the fused sulfur ring units based on total units in the polymer.
Particularly sulfur ring polymer units include those that have five, six or seven ring members and an sulfur ring member adjacent to the polymer backbone, such as units of the following Formula IIA: 
wherein Y is the same as specified for Formula I above;
wherein each Zxe2x80x2 is independently carbon, oxygen, or sulfur; and preferably is Zxe2x80x2 is carbon; mxe2x80x2 is 1, 2, 3 or 4; and R and n are each the same as defined in Formula I above, and preferably n is 0, 1, 2, 3, 4 or 5, and more preferably n is 0, 1, 2 or 3; and
p is greater than zero and is the mole fraction of the fused sulfur ring units based on total units in the polymer.
Polymers of the invention also may contain oxygen or sulfur ring groups that are spaced from the polymer backbone. The spaced oxygen or sulfur ring group suitably will contain a single ring, although polycyclic rings that contain one or more oxygen or sulfur ring members also will be suitable. Less preferred are groups where sulfur or oxygen is a bridgehead atom of a polycyclic group, particularly a bridgehead of a bicyclic group such as a oxonorbornyl or thionorbonyl group, especially if such oxonorbornyl or thionorbonyl group is present as part of an ester moiety.
For example, suitable spaced oxygen and/or sulfur ring groups of polymer of the invention include those of the following Formula III: 
wherein W is a linker; X, Y, and each Z are each independently carbon, oxygen, or sulfur, with at least one of X, Y or Z being oxygen or sulfur;
each R is the same or different non-hydrogen substituent such as those non-hydrogen substituents specified for R in Formula I above;
m is 1, 2, 3, 4 or 5; n is an integer of from 0 to the maximum value substitution permitted by the valences of the ring members; and p is the mole percent of the units in the polymer.
Typical W linker groups of Formula III include e.g. optionally substituted alkylene particularly optionally substituted C1-8 alkylene; optionally substituted alkenylene particularly optionally substituted C2-8 alkenylene; optionally substituted alkynylene particularly optionally substituted C2-8 alkynylene; optionally substituted heteroalkylene particularly optionally substituted C1-8 heteroalkylene; optionally substituted heteroalkenylene particularly optionally substituted C2-8 heteroalkenylene; optionally substituted heteroalkynylene particularly optionally substituted C2-8 heteroalkynylene; an ester linkage (i.e. xe2x80x94C(xe2x95x90O)O); and the like. In Formula III, the spaced oxygen or sulfur ring group may be a component of a photoacid-labile group, such as a photoacid-labile ester group. Such groups may be provided by polymerization of the corresponding acrylate or methacrylate groups.
Preferably, a sulfur heteroalicyclic group will be present in a polymer with polymerized carbon alicyclic olefin compounds. More specifically, preferred polymers of the invention include those that comprise a structure of the following Formula IV: 
wherein X, Y, Z, R, m, n and p are each the same as defined in Formula II above;
Q and r are the same as defined for Formula I above.
Preferred carbon alicyclic ring units are polymerized optionally substitutednorbornene groups. Thus, preferred polymers that contain sulfur heteroalicyclic units comprise a structure of the following Formula IVA: 
wherein X, Y, Z, R, m and n are the same specified for Formula II above;
R1 and R2 are the same as defined in Formula IA above;
p is the mole fraction of the fused sulfur ring units based on total units in the polymer; and r is the mole fraction of the fused optionally substituted norbornene ring units based on total units in the polymer, and p and r are each greater than zero.
Particularly preferred sulfur ring polymer units include those that have five, six, seven or eight ring members and a sulfur ring member adjacent to the polymer backbone. Accordingly, preferred are polymers that comprise a structure of the following Formula IVB: 
wherein each Zxe2x80x2 is independently oxygen, sulfur or carbon, and preferably is carbon; mxe2x80x2 is 1, 2, 3 or 4; and R and n are each the same as defined in Formula I above, and preferably n is 0, 1, 2, 3, 4 or 5, and more preferably n is 1, 2 or 3;
Q is the same as defined in Formula I;
p is the mole fraction of the fused sulfur ring units based on total units in the polymer; and r is the mole fraction of the fused carbon alicyclic ring units based on total units in the polymer, and p and r are each greater than zero.
Preferred polymers of Formula IVB contain polymerized norbornene units, e.g.polymers that comprise a structure of the following Formula IVC: 
wherein Zxe2x80x2, mxe2x80x2, R, n, and p are the same as defined in Formula IVB; and
R1, R2 and r are the same as defined in Formula IA.
In the above Formulae I, IA, IB, IC, II, IIA, III, IV, IVA, IVB and IVC, and the below Formulae V, VI and VII (together sometimes referred to herein simply as xe2x80x9cthe formulaexe2x80x9d or similar phrase), preferably R substituents of the depicted heteroalicyclic unit are electron-donating groups such as optionally substituted alkyl, optionally substituted alkoxy or optionally substituted alkylthio. Such electron-donating groups can facilitate polymerization of the corresponding vinyl heteroalicyclic monomer.
Preferred polymers of the invention will contain at least about 2 to 5 mole percent of fused heteroalicyclic units based on total units of the polymer; more preferably from about 5 to 50 mole percent of fused heteroalicyclic units based on total units of the polymer; still more preferably from about 5 or 10 to about 40 or 50 percent of fused heteroalicyclic units based on total units of the polymer.
Preferred polymers of the invention will contain at least about 2 to 5 mole percent of carbon alicyclic units based on total units of the polymer; more preferably from about 5 to 50 mole percent of fused carbon alicyclic units based on total units of the polymer; still more preferably from about 5 or 10 to about 25 or 30 percent of fused carbon alicyclic units based on total units of the polymer.
In polymers of the invention that contain only heteroalicyclic units and carbon alicyclic units, preferably the heterocyclic units will be present in an amount of from about 5 to about 90 or 95 mole percent based on total polymer units, and the carbon alicyclic units will be present in an amount of from about 5 to about 90 or 95 mole percent based on total polymer units.
In polymers of the invention that consist of heteroalicyclic units, carbon alicyclic units and maleic anhydride units (i.e. heteroalicyclic:carbon alicyclic:maleic anhydride terpolymers), preferably the heterocyclic units will be present in an amount of from about 5 to about 10, 20, 30, 40, 50, 60, 70 or 80 mole percent based on total polymer units, the carbon alicyclic units (such as optionally substituted norbornene) will be present in an amount of from about 5 to about 10, 20, 30, 40, 50, 60, 70 or 80 mole percent based on total polymer units, and the maleic anhydride units will be present from about 5 to about 20, 30, 40 or 50 mole percent based on total polymer units; and more preferably the heterocyclic units will be present in an amount of from about 5 to about 10, 20, 30, 40, 50 or 60 mole percent based on total polymer units, the carbon alicyclic units will be present in an amount of from about 5 to about 10, 20, 30, 40, 50 or 60 mole percent based on total polymer units, and the maleic anhydride units will be present from about 5 to about 10, 15, 20, 25, 30, 40, or 50 mole percent based on total polymer units. In such terpolymers, suitably either or both the heteroalicyclic or carbon alicyclic units will contain a photoacid labile substituents such as a photoacid-labile ester substituent.
In the above the above formulae, the R, R1 and R2 substituents each can be photoacid-labile groups. Photoacid-labile ester groups are generally preferred such as a tert-butyl ester, or an ester containing a tertiary alicyclic group. Such photoacid-labile esters may be directly pendant from a heteroalicyclic or carbon alicyclic polymer unit (i.e. xe2x80x94C(xe2x95x90O)OR, where R is tert-butyl or other non-cyclic alkyl group, or a tertiary alicyclic group), or the ester moieties may be spaced from the from a heteroalicyclic or carbon alicyclic polymer unit, e.g. by an optionally alkylene linkage (e.g. xe2x80x94(CH2)1-8C(xe2x95x90O)OR, where R is is tert-butyl or other non-cyclic alkyl group, or a tertiary alicyclic group).
In any event, polymers of the invention preferably comprise contain one or more repeat units that comprise a photoacid-labile group. As discussed with respect to substituents R, R1 and R2 of the above formulae, the photoacid-labile may be a substituent of a heteroalicyclic or carbon alicyclic ring member. Alternatively, and generally preferred, the photoacid-labile moiety will be a polymer repeat unit distinct from repeat units containing a heteroalicyclic group.
Preferred photoacid-labile groups are ester groups, particularly esters that contain a tertiary alicyclic hydrocarbon ester moiety. Preferred tertiary alicyclic hydrocarbon ester moieties are polycyclic groups such adamantyl, ethylfencyl or a tricyclo decanyl moiety. References herein to a xe2x80x9ctertiary alicyclic ester groupxe2x80x9d or other similar term indicate that a tertiary alicyclic ring carbon is covalently linked to the ester oxygen, i.e. xe2x80x94C(xe2x95x90O)Oxe2x80x94TRxe2x80x2 where T is a tertiary ring carbon of alicyclic group Rxe2x80x2. In at least many cases, preferably a tertiary ring carbon of the alicyclic moiety will be covalently linked to the ester oxygen, such as exemplified by the below-depicted specifically preferred polymers. However, the tertiary carbon linked to the ester oxygen also can be exocyclic to the alicyclic ring, typically where the alicyclic ring is one of the substituents of the exocyclic tertiary carbon. Typically, the tertiary carbon linked to the ester oxygen will be substituted by the alicyclic ring itself, and/or one, two or three alkyl groups having 1 to about 12 carbons, more typically 1 to about 8 carbons, even more typically 1, 2, 3 or 4 carbons. The alicyclic group also preferably will not contain aromatic substitution. The alicyclic groups may be suitably monocyclic, or polycyclic, particularly bicyclic or tricyclic groups.
Preferred alicyclic moieties (e.g. group TRxe2x80x2 of xe2x80x94C(xe2x95x90O)Oxe2x80x94TRxe2x80x2) of photoacid labile ester groups of polymers of the invention have rather large volume. It has been found that such bulky alicyclic groups can provide enhanced resolution when used in copolymers of the invention.
More particularly, preferred alicyclic groups of photoacid labile ester groups will have a molecular volume of at least about 125 or about 130 xc3x853, more preferably a molecular volume of at least about 135, 140, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, or 200 xc3x853. Alicyclic groups larger than about 220 or 250 xc3x853 may be less preferred, in at least some applications. References herein to molecular volumes designate volumetric size as determined by standard computer modeling, which provides optimized chemical bond lengths and angles. A preferred computer program for determining molecular volume as referred to herein is Alchemy 2000, available from Tripos. For a further discussion of computer-based determination of molecular size, see T Omote et al, Polymers for Advanced Technologies, volume 4, pp. 277-287.
Particularly preferred tertiary alicyclic groups of photoacid-labile units include the following, where the wavy line depicts a bond to the carboxyl oxygen of the ester group, and R is suitably optionally substituted alkyl, particularly C1-8 alkyl such as methyl, ethyl, etc. 
Polymers of the invention also may contain photoacid-labile groups that do not contain an alicyclic moiety. For example, polymers of the invention may contain photoacid-labile ester units, such as a photoacid-labile alkyl ester. Generally, the carboxyl oxygen (i.e. the carboxyl oxygen as underlined as follows: xe2x80x94C(xe2x95x90O)O) of the photoacid-labile ester will be covalently linked to the quaternary carbon. Branched photoacid-labile esters are generally preferred such as t-butyl and xe2x80x94C(CH3)2CH(CH3)2.
Polymers of the invention also may contain additional units such as cyano units, lactone units or anhydride units. For example, acrylonitrile or methacrylonitrile may be polymerized to provide pendant cyano groups, or maleic anhydride may be polymerized to provide a fused anhydride unit.
Particularly preferred polymers of the invention include those that comprise a structure of the following Formula V: 
wherein X, Y, Z, R, m and n are each the same as defined in Formula I above;
R1 and R2 are each independently hydrogen or a non-hydrogen substituent such as specified for R1 and R2 in Formula IA above;
R3 is hydrogen or alkyl, particularly C1-6 alkyl such as methyl;
R4 is a group that renders the depicted ester photoacid-labile, such as a tertiary alicyclic group as discussed above, or a branched non-cyclic optionally substituted alkyl group, with the ester carboxyl group being directly bonded to a quaternary (i.e. no hydrogen substituents) carbon atom; and
a, b, c, and d are each greater than zero and are mole fractions of the respective polymer units.
Preferred polymers of the invention also include those of the following Formula VI: 
wherein X, Y, Z, R, m and n are each the same as defined in Formula II above;
R1 and R2 are each independently hydrogen or a non-hydrogen substituent such as such as specified for R1 and R2 in Formula IA above;
R3 is hydrogen or alkyl, particularly hydrogen or C1-6 alkyl such as methyl;
R4 is a group that renders the depicted ester photoacid-labile, such as a tertiary alicyclic group as discussed above, or a branched non-cyclic optionally substituted alkyl group, with the ester carboxyl group being directly bonded to a quaternary (i.e. no hydrogen substituents) carbon atom; and
a, b, c, and d are each greater than zero and are mole fractions of the respective polymer units.
In each of above Formulae V and VI, preferably xe2x80x9caxe2x80x9d (mole fraction of heterocyclic units) is from about 2 to 50 mole percent based on total polymer units; more preferably xe2x80x9caxe2x80x9d is from about 2 to about 40 mole percent based on total polymer units; and still more preferably xe2x80x9caxe2x80x9d is from about 2 to about 30 mole percent based on total polymer units.
In each of above Formulae V and VI, preferably xe2x80x9cbxe2x80x9d (mole fraction of norbornene units) is from about 2 to 25 mole percent based on total polymer units; more preferably xe2x80x9cbxe2x80x9d is from about 2 to about 20 mole percent based on total polymer units; and still more preferably xe2x80x9cbxe2x80x9d is from about 2 to about 15 or 20 mole percent based on total polymer units.
In each of above Formulae V and VI, preferably xe2x80x9ccxe2x80x9d (mole fraction of anhydride units) is from about 0 (i.e. no anhydride units) to 50 mole percent based on total polymer units; more preferably xe2x80x9ccxe2x80x9d is from about 2 to about 40 mole percent based on total polymer units.
In each of above Formulae V and VI, preferably xe2x80x9cdxe2x80x9d (mole fraction of photoacid-labile ester unit) is from about 2 to 70 mole percent based on total polymer units; more preferably xe2x80x9cdxe2x80x9d is from about 5 or 10 to about 70 mole percent based on total polymer units; still more preferably xe2x80x9cdxe2x80x9d is from about 5 or 10 to about 50 mole percent based on total polymer units.
Preferred heteroalicyclic units of Formulae V and VI are the same as described above regarding Formulae IA and IIA respectively.
As discussed above, polymers of the invention are preferably employed in photoresists imaged at short wavelengths, particularly sub-200 nm such as 193 nm and 157 nm. Polymers also can be employed in photoresists imaged at higher wavelengths such as 248 nm. For such higher wavelength applications, the polymer may suitably contain aromatic units, e.g. polymerized styrene or hydrostyrene units.
Specifically preferred polymers of the invention include those of the following Formula VII: 
In Formula VII above, xe2x80x9cAlicyclic LGxe2x80x9d is the same as defined for alicyclic substituent R4 in Formulae V and VI above and is preferably methyladamantyl, 8-ethyl-8-tricyclodecanyl, ethylfencyl and the like; R1 is C1-8 alkyl, preferably C1-4 alky, o9r a moietty that forms a photoacid-labile group; R2 is suitably hydrogen or C1-8 alkyl, such as methyl, ethyl, propyl and the like; R1 and R2 are the same as defined for R1 and R2 respectively in Formula IA above; and a, b, c and d are mole percents of the specified units in the polymer based on total polymer units. Preferably a (mole percent of oxygen alicyclic units) is from 1 to about 5, 10, 20, 30, 40, 50 or 60 mole percent; b (mole percent of optionally substituted norbornene units) is from 1 to about 5, 10, 20, 30, 40, 50 or 60 mole percent; c (mole percent of maleic anhydride units) is from 1 to about 5, 10, 20, 30, 40, or 50 mole percent. Units d (acrylate photoacid-labile units) may be not be present (i.e. d is zero) where the heterocyclic or norbornene units contain a photoacid-labile units, or d may be suitably present at from about 2 to 10, 20, 30, 40 or 50 mole percent based on total polymer units.
As discussed, various moieties may be optionally substituted, including groups of Formulae I, IA, II, IIA, III, IV, IVA, IVB, IVC, V, VI, and VII. A xe2x80x9csubstitutedxe2x80x9d substituent may be substituted at one or more available positions, typically 1, 2, or 3 positions by one or more suitable groups such as e.g. halogen (particularly F, Cl or Br); cyano; C1-8 alkyl; C1-8 alkoxy; C1-8 alkylthio; C1-8 alkylsulfonyl; C2-8 alkenyl; C2-8 alkynyl; hydroxyl; nitro; alkanoyl such as a C1-6 alkanoyl e.g. acyl and the like; etc.
Preferred alkanoyl groups, including as specified in the above formulae, will have one or more keto groups, such as groups of the formula xe2x80x94C(xe2x95x90O)Rxe2x80x3 where Rxe2x80x3 is hydrogen or C1-8 alkyl. Suitable lactone groups, including as specified in the above formulae, include alpha-butyrolactone groups and the like.
Polymers of the invention can be prepared by a variety of methods. One suitable method is an addition reaction which may include free radical polymerization, e.g., by reaction of selected monomers to provide the various units as discussed above in the presence of a radical initiator under an inert atmosphere (e.g., N2 or argon) and at elevated temperatures such as about 70xc2x0 C. or greater, although reaction temperatures may vary depending on the reactivity of the particular reagents employed and the boiling point of the reaction solvent (if a solvent is employed). Suitable reaction solvents include e.g. tetrahydrofaran, ethyl lactate and the like. Suitable reaction temperatures for any particular system can be readily determined empirically by those skilled in the art based on the present disclosure. A variety of free radical initiators may be employed. For example, azo compounds may be employed such as azo-bis-2,4-dimethylpentanenitrile. Peroxides, peresters, peracids and persulfates also could be employed.
Other monomers that can be reacted to provide a polymer of the invention can be identified by those skilled in the art. For example, to provide photoacid-labile units, suitable monomers include e.g. methacrylate or acrylate that contains the appropriate group substitution (e.g. tertiary alicyclic, t-butyl, etc.) on the carboxy oxygen of the ester group. Maleic anhydride is a preferred reagent to provide fused anhydride polymer units. Itaconic anhydride also is a preferred reagent to provide anhydride polymer units, preferably where the itaconic anhydride has purified such as by extraction with chloroform prior to polymerization. Vinyl lactones are also preferred reagents, such as, alpha-butyrolactone.
Some suitable vinyl (endocyclic double bond) heterocyclic monomers that can be polymerized to provide polymers of the invention include the following: 
Preferably a polymer of the invention will have a weight average molecular weight (Mw) of about 800 or 1,000 to about 100,000, more preferably about 2,000 to about 30,000, still more preferably from about 2,000 to 15,000 or 20,000, with a molecular weight distribution (Mw/Mn) of about 3 or less, more preferably a molecular weight distribution of about 2 or less. Molecular weights (either Mw or Mn) of the polymers of the invention are suitably determined by gel permeation chromatography.
Polymers of the invention used in photoresist formulations should contain a sufficient amount of photogenerated acid labile ester groups to enable formation of resist relief images as desired. For instance, suitable amount of such acid labile ester groups will be at least 1 mole percent of total units of the polymer, more preferably about 2 to 50 mole percent, still more typically about 3 to 30 or 40 mole percent of total polymer units. See the examples which follow for exemplary preferred polymers.
As discussed above, the polymers of the invention are highly useful as a resin binder component in photoresist compositions, particularly chemically-amplified positive resists. Photoresists of the invention in general comprise a photoactive component and a resin binder component that comprises a polymer as described above.
The resin binder component should be used in an amount sufficient to render a coating layer of the resist developable with an aqueous alkaline developer.
The resist compositions of the invention also comprise a photoacid generator (i.e. xe2x80x9cPAGxe2x80x9d) that is suitably employed in an amount sufficient to generate a latent image in a coating layer of the resist upon exposure to activating radiation. Preferred PAGs for imaging at 193 nm and 248 nm imaging include imidosulfonates such as compounds of the following formula: 
wherein R is camphor, adamantane, alkyl (e.g. C1-12 alkyl) and perfluoroalkyl such as perfluoro(C1-12alkyl), particularly perfluorooctanesulfonate, perfluorononanesulfonate and the like. A specifically preferred PAG is N-[(perfluorooctanesulfonyl)oxy]-5-norbornene-2,3-dicarboximide.
Sulfonate compounds are also suitable PAGs, particularly sulfonate salts. Two suitable agents for 193 nm and 248 nm imaging are the following PAGS 1 and 2: 
Such sulfonate compounds can be prepared as disclosed in European Patent Application 96118111.2 (publication number 0783136), which details the synthesis of above PAG 1.
Also suitable are the above two iodonium compounds complexed with anions other than the above-depicted camphorsulfonate groups. In particular, preferred anions include those of the formula RSO3xe2x80x94 where R is adamantane, alkyl (e.g. C1-12 alkyl) and perfluoroalkyl such as perfluoro (C1-12alkyl), particularly perfluorooctanesulfonate, perfluorobutanesulfonate and the like.
Other known PAGS also may be employed in the resists of the invention. Particularly for 193 nm imaging, generally preferred are PAGS that do not contain aromatic groups, such as the above-mentioned imidosulfonates, in order to provide enhanced transparency.
A preferred optional additive of resists of the invention is an added base, particularly tetrabutylammonium hydroxide (TBAH), or tetrabutylammonium lactate, which can enhance resolution of a developed resist relief image. For resists imaged at 193 nm, a preferred added base is a hindered amine such as diazabicyclo undecene or diazabicyclononene. The added base is suitably used in relatively small amounts, e.g. about 0.03 to 5 percent by weight relative to the total solids.
Photoresists of the invention also may contain other optional materials. For example, other optional additives include anti-striation agents, plasticizers, speed enhancers, etc. Such optional additives typically will be present in minor concentrations in a photoresist composition except for fillers and dyes which may be present in relatively large concentrations, e.g., in amounts of from about 5 to 30 percent by weight of the total weight of a resist""s dry components.
The resists of the invention can be readily prepared by those skilled in the art. For example, a photoresist composition of the invention can be prepared by dissolving the components of the photoresist in a suitable solvent such as, for example, ethyl lactate, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether; propylene glycol monomethyl ether acetate and 3-ethoxyethyl propionate. Typically, the solids content of the composition varies between about 5 and 35 percent by weight of the total weight of the photoresist composition. The resin binder and photoactive components should be present in amounts sufficient to provide a film coating layer and formation of good quality latent and relief images. See the examples which follow for exemplary preferred amounts of resist components.
The compositions of the invention are used in accordance with generally known procedures. The liquid coating compositions of the invention are applied to a substrate such as by spinning, dipping, roller coating or other conventional coating technique. When spin coating, the solids content of the coating solution can be adjusted to provide a desired film thickness based upon the specific spinning equipment utilized, the viscosity of the solution, the speed of the spinner and the amount of time allowed for spinning.
The resist compositions of the invention are suitably applied to substrates conventionally used in processes involving coating with photoresists. For example, the composition may be applied over silicon wafers or silicon wafers coated with silicon dioxide for the production of microprocessors and other integrated circuit components. Aluminum-aluminum oxide, gallium arsenide, ceramic, quartz, copper, glass substrates and the like are also suitably employed.
Following coating of the photoresist onto a surface, it is dried by heating to remove the solvent until preferably the photoresist coating is tack free. Thereafter, it is imaged through a mask in conventional manner. The exposure is sufficient to effectively activate the photoactive component of the photoresist system to produce a patterned image in the resist coating layer and, more specifically, the exposure energy typically ranges from about 1 to 100 mJ/cm2, dependent upon the exposure tool and the components of the photoresist composition.
As discussed above, coating layers of the resist compositions of the invention are preferably photoactivated by a short exposure wavelength, particularly a sub-300 and sub-200 nm exposure wavelength. As discussed above, 193 nm is a particularly preferred exposure wavelength. 157 nm also is a preferred exposure wavelength. However, the resist compositions of the invention also may be suitably imaged at higher wavelengths. For example, a resin of the invention can be formulated with an appropriate PAG and sensitizer if needed and imaged at higher wavelengths e.g. 248 nm or 365 nm.
Following exposure, the film layer of the composition is preferably baked at temperatures ranging from about 70xc2x0 C. to about 160xc2x0 C. Thereafter, the film is developed. The exposed resist film is rendered positive working by employing a polar developer, preferably an aqueous based developer such as quaternary ammonium hydroxide solutions such as a tetra-alkyl ammonium hydroxide solution; various amine solutions preferably a 0.26 N tetramethylammonium hydroxide, such as ethyl amine, n-propyl amine, diethyl amine, di-n-propyl amine, triethyl amine, or methyldiethyl amine; alcohol amines such as diethanol amine or triethanol amine; cyclic amines such as pyrrole, pyridine, etc. In general, development is in accordance with procedures recognized in the art.
Following development of the photoresist coating over the substrates the developed substrate may be selectively processed on those areas bared of resist, for example by chemically etching or plating substrate areas bared of resist in accordance with procedures known in the art. For the manufacture of microelectronic substrates, e.g., the manufacture of silicon dioxide wafers, suitable etchants include a gas etchant, e.g. a halogen plasma etchant such as a chlorine or fluorine-based etchant such a Cl2 or CF4/CHF3 etchant applied as a plasma stream. After such processing, resist may be removed from the processed substrate using known stripping procedures.